Tsuguru Shirakawa

A Study of Magnetophonon Effect in n -InSb Using Field Modulation Technique

Precise measurements of the magnetophonon effect in n -InSb are made by making use of a magnetic field modulation and phase sensitive second harmonic detection technique. Obtained data show an excellent signal to noise ratio and up to the 14th extremum are resolved in the transverse configuration at 77 K. Second derivative of the magnetoresistance in the longitudinal configuration is extensively investigated in the temperature range of 89 to 171 K. A curve resolver analysis is applied to resolve new structure which appears between the ordinary magnetophonon resonance peaks and four peaks around the N =2 peak are resolved, which are assigned to the structure arising from the spin-conserving single and two LO phonon processes. Fourier transform technique is also adopted to obtain frequency spectrum of the magnetophonon structure. The higher harmonic terms and two LO phonon components are resolved for the first time by using a proper window function for Fourier analysis. The results are consistent with those...

Magnetophonon Resonance of Hot Electrons in n -InSb at 77 K

Magnetophonon resonances, which were first predicted by Gurevich and Firsov, have been observed in the hot electron mobility in pure n -InSb. The resonance experiment was carried out at 77 K in transverse magnetic field up to 22 kG with application of sufficiently small electric field to produce a slight change in the electron mobility. The quantity β in the formula µ=µ 0 (1-β E 2 ) was measured with extremely good accuracy ( Δ µ/µ 0 ∼10 -7 ) by adopting a bridge circuit. The minima in the quantity |β| were observed at magnetic fields, B =17.5, 11.3, 8.53, 6.89, 5.72, 4.83, 4.12, 3.68, 3.72, and 2.93 kG. These resonance extrema are attributed to resonant cooling of hot electrons due to optical phonon induced transitions from the high energy tail of the electron distribution near k z =0 at higher Landau levels to lower Landau levels. The extremal positions are well explained by taking the non-parabolicity of the conduction band of InSb into account.

New series of the magnetophonon resonance under hot electron conditions in n-InSb

Abstract Measurements of the magnetophonon resonance in n -InSb under hot electron conditions are performed for the longitudinal configuration over a wide range of temperatures. Besides the ordinary one-phonon series, new minima are observed at magnetic field where two-phonon process is expected.

Structure of magnetophonon resonance under hot electron condition in n-InSb

Abstract The complex structure observed in the hot electron magnetophonon resonance is tentatively explained by using an empirical formula based upon Lorentzian functions, where spin conserving single-phonon and two-LO-phonon scatterings are taken into account.

Pressure dependence of Raman modes in ZnSiP2 crystal

SummaryThe hydrostatic-pressure dependence of the first-order Raman spectra in the ZnSiP2 crystal has been measured up to 52 kbar and the Grüneisen parameter of each Raman mode was obtained. Phonon modes observed in the ZnSiP2 crystal can be classified into five groups according to the value of the Grüneisen mode parameter. The correspondence between Raman modes in ZnSiP2 and those in its binary analog GaP was elucidated by comparing Grüneisen parameters in the two crystals. From such a correspondence, complicated lattice vibration modes in ZnSiP2 were made clear.RiassuntoLa dipendenza degli spettri di Raman di primo ordine dalla pressione idrostatica in cristalli di ZnSiP2 è stata misurata fino a 52k bar e il parametro di Grüneisen di ogni modo di Raman è stato ottenuto. I modi fononici osservati nel cristallo di ZnSiP2 possono essere classificati in cinque gruppi secondo il valore del parametro di Grüneisen del modo. La corrispondenza tra modi di Raman in ZnSiP2 e quelli nel suo analogo binario GaP è stata chiarita confrontando i parametri di Grüneisen nei due cristalli. Da tale corrispondenza sono stati chiariti complicati modi di vibrazione reticolare in ZnSiP2.РезюмеИзмеряется зависимость от гидростатического давления вплоть до 52 кбар Рамановских спектров пектров первого порядка в кристаллах ZnSiP2. Для каждой Рамановской моды получен параметр Грюнайзена. Наблюденные фононные моды в кристалле ZnSiP2 могут быть классифицированы а пять групп, соответственно параметру Грюнайзена. Объясняется соответствие между Рамановскими модами в ZnSiP2 и Рамановскими модами в бинарном аналоге GaP, посредством сравнения параметров Грюнайзена в двух кристаллах. Это соответветствие проясняет сложные моды колебаний решетки в ZnSiP2.

Pressure dependence of pseudo-direct gaps in ZnSiP2

Abstract Hydrostatic-pressure dependence of pseudo-direct gaps in ZnSiP 2 has been measured at room temperature under pressures up to 23.6 kbar. The pressure coefficient of the lowest conduction band Γ c 6 is very close to that of the indirect X 1 band in A III B V semiconductors.

Observation of Luminescent Lines Related to Pseudodirect Gap in ZnSiP2 Crystals

The photoluminescence of ZnSiP2 crystals has been measured at 4.2 K. New sharp emission lines were observed at about 1.980 eV in a sample annealed at 400°C in vacuum. The intensity of these lines is greatly enhanced by excitation at the exciton absorption peak associated with the pseudodirect gap. This indicates that these emission lines are due to the bound excitons associated with the pseudodirect gap, in contrast to the results of previous photoluminescence measurements suggesting that this crystal is an indirect-gap semiconductor.

Photovoltaic effect of ZnSiP2 crystals from Zn melt

Abstract The photovoltage of an InZnSiP 2 Schottky diode has been measured as a function of the excitation photon energy. Three sharp peaks, which cannot be attributed to band-band transitions, have been observed for the first time near the band edge of the photovoltage spectrum.

Observation of Landau Levels and Two-Dimensional Energy Bands in CdSnAs2 by Electron Tunneling

By tunneling measurements, it has been demonstrated experimentally, for the first time, that surface bound states of electrons localized in an accumulation layer exist at the CdSnAs2-oxide interface. In a CdSnAs2-oxide-Pb junction whose semiconductor electrode has a carrier concentration n=4.4×1018/cm3, the binding energies of the ground and the excited states are 44 meV and 16 meV, respectively. The Landau level structure of the two-dimensional energy band associated with the excited bound state has been observed in magnetic fields up to 55 kG. The effective mass of the electric subband is found to be m0*=(0.019±0.002)m0.

Phonon-Assisted Tunneling in Metal-Oxide-Pb1-xSnxTe Junctions

Electron tunneling effects of Pb 1- x Sn x Te are investigated in M-I-S junctions. Phonon-assisted tunneling effects are observed in the d 2 I /d V 2 - V characteristics. Assignments of four peaks which appear antisymmetric with respect to zero bias in the d 2 I /d V 2 - V characteristics are made by measuring the composition-dependence of energy positions of these peaks. These assignments are examined from the group theoretical point of view. The energies of the LO phonons at \(\varGamma\) point are 14.3±0.5 meV for PbTe and 17.1±0.5 meV for SnTe, which are in good agreement with the results obtained by the other methods.